Thermal infrared mapping of White Island volcano, New Zealand

The first aerial thermal infrared (TIR) survey of White Island volcano was successfully performed during the early morning of 15 April 1992. High spatial resolution (1-2 m) TIR imagery, representative of surface temperatures, and simultaneous visible video imagery were obtained over approximately 75% of the exposed portion of this active volcano. Surface temperatures, ranging from ambient (11.8 degrees C) to active (95.7 degrees C), were measured at 12 sites for image calibration purposes. The TIR imagery clearly depicts structurally complex thermal areas within Main Crater. Regions of thermal activity along the northern crater rim and on the northwest, north and northeast crater flanks were also detected. One thermal seepage was observed on the north coast, west of North East Point. A close correlation is demonstrated between the TIR thermal anomalies and present vent locations, prehistoric subcrater boundaries, and the geohydrology of the hydrothermal system hosted in Main Crater. Most of the active 1978/90 Crater Complex was mapped as a high-temperature anomaly, except for one relatively cool area which developed soon after by subsidence and collapse into a major new vent, Princess Crater. Impermeable crater lake sediments are believed to cap the hydrothermal system in parts of the central and eastern subcraters where the TIR map shows appreciable areas at ambient temperatures. An area of high heat flow is located in the south side of the eastern subcrater where steam and gas escape through fractured lavas. The distribution of thermal anomalies in the eastern subcrater suggests that there may have been two smaller craters located within the larger, now filled in, structure.